#include <iostream>
#include <cstdio>
using namespace std;

int getNum(int n)
{
    int a = 0;
    int b = 1;
    int c = 0;
    while (--n)
    {
        c = a + b;
        a = b;
        b = c;
    }
    return c;
}
int main() {
    int n;
    cin >> n;
    cout << getNum(n) << endl;
    return 0;
}